Urinary Excretion of Formiminoglutamic Acid by Human Subjects after Antifolic Acid Therapy1

In the accompanying paper a sensitive and spe-cific enzymatic method is described for the meas-urement of formiminoglutamic acid (1). In this paper data are presented on the application of this method for the assay of formiminoglutamic acid in the urine of a variety of patients. Formiminoglutamic acid is an intermediate in histidine metabolism, and requires tetrahydrofolic acid for its further metabolism. Previous results (2-5) have demonstrated that the urinary excre-tion of this compound is markedly increased in folic acid-deficient rats. Formiminoglutamic acid has also been reported (6, 7) in the urine of sev-eral patients receiving folic acid antagonists, al-though the techniques available for these studies